Method of compacting carbon black



Aug. 7, 1956 H. s. BARBOUR METHOD OF COMPACTING CARBON BLACK Filed March17, 1954 United States atent METHOD 0F COMPACTING 'C'ARBON BLACK HarryS. Barbour, Borger, Tex., assignor to J. M. Huber Corporation, Borger,Tex., a corporation of New Jersey Application March 17, 1954, Serial No.416,816 5 Claims. (Cl. 117-100) This invention relates to carbon blackand particularly to a method for converting lluify carbon into the formof relatively dustless `and free flowing pellets.

Carbon black when originally collected from either channel or furnaceplants is in the form of an extremely line powder weighing about fourpounds per cubic foot. The powder occludes a large amount of air and isextremely ilutfy. It sometimes is agitated in'order to remove some `ofthe occluded air, until its weight is from 8 to l2 pounds per cubicfoot, :but fluffy carbon treated in that manner still is troublesome andexpensive to package and transport, and it also creates a dust nuisancein handling.

This problem has been dealt with by converting carbon black into densegranules, usually designated as compacted carbon, which weigh from about-1'8 to 26 pounds per cubic foot. One method of producing compactedcarbon is illustrated by U. S. Patents Nos. 2,065,371 and 2,131,686. Inaccordance with those patents, flulfy carbon is mixed with from 35 to65% of its weight of water, or sutdcient to produce a paste, and thepas-ty mixture is beaten with pins attached to a rotating shaft untilthe mass is formed into small granules. The granules are then dried inan externally heated rotated drum, and in the course of this processthey become somewhat rounded and are formed into a relatively dustlessand free-flowing granular mass.

A second known method, one Which employs no water or other liquid, isdescribed in U. S. Patent 2,164,164. In that method the fluffy carbon isintroduced into one end of a slowly rotating drum in which it is rolledand tumbled until it has the fform of small rounded pellets.

Since the introduction of free flowing compacted carbon to the trade,much of the carbon of commerce has been converted to a compacted formand transported in bulk in tank cars. The carbon pellets must besufficiently strong to resist breakage and dust formation during theseveral handling steps involved from the time of their production untilthey are ready to be incorporated into end products such as rubbercompounds, paints, inks, or the like. When their structural strength isinsucient, difficulty is encountered, for example, in the dilferentweighing, conveying and other machines utilized for the handling ofcarbon black in the rubber industry. In general, it can be said thatpelletsproduced by a Wet method are more rm and dust Ifree than pelletsproduced by the dry method. On the other hand, the wet process pelletsare so tirm that they resist disintegration in rubber, and they haverubber reinforcing properties inferiorto those of carbon compacted by adry method. The wet method is also more costly because it usuallyrequires the evaporation of an amount of Water almost lequal to that ofthe carbon.

An object of this invention is to provide a new and improved method torthe preparation of compacted carbon.

A further object is to provide a compacted carbon which is sufcientlyt'irm to be transported satisfactorily but will still disintegrate anddisperse satisfactorily in rubber.

When a single pellet of compacted carbon is dropped into Water itabsorbs water in the manner of a sponge and' during the attendantswelling process it is broken into fragments.

2,758,039 Patented Aug. 7, 1956 ICC I have now found that water may beadded in the form of a ne spray to a moving mass of compacted carbonwithout breaking the pellets and with the result that only the surfacelayer of the pellets absorbs water. According to 'this invention, theobjects mentioned above can 'be achieved by lirst compacting fluffycarbon Iby 'a dry process of the character described above, thenspraying the surface of a moving mass of the compacted carbon pellets ina rotating drum `with a limited -amount yof water suicient to absorbwater into only the surface layer of the pellets and to cause the dustto adhere to the surface of the pellets, and then drying the resultingproduct. In this manner I am able to produce pellets the inside of whichhas never been wetted and therefore is easily dispersible in rubber,while the surfaces of the pellets are suciently trm to produce strongpellets. A further advantage of this process is that the yamount ofwater to be evaporated is only a fraction of that employed in the usualwet methods.

The carbon to be treated according to this invention should first becompacted by a dry method so that the pellets weigh at least about 18pounds per cubic foot and the dust content is less than about 20% of theweight of the carbon. vIf the pellets are not suciently compacted toweigh yabout 18 pounds per cubic foot they lare liable to disintegrateunder the treatment. If the dust content is `over 20% an excessiveamount of water is required to collect it, and the mass is liable tobecome pasty. Good f Howard W. Price, with or without the `aid ofrolling coml pression members. The dry compacted carbon so formed,containing the usual amount of dust, is then passed to a second rotatingdrum where it is sprayed with 5% to 25% of its weight of water while thecarbon is maintained in motion. The amount of water is limited i in sucha manner that the granules of compacted carbon do not become sucientlymoistened to adhere to each other. This generally is vfound to be notover 25%, and in most cases considerably less than 25 is effective toproduce an improved form of pellet. For example, a tine water sprayequivalent to about =15% `of the Weight of the mass of compacted carbonusually gives vexcellent results.

The rolling motion of the superficially moistened compacted carbonpellets in the rotating drum causes them to pick up rapidly the residueof dusty carbon contained in the mass. The resulting moistened andrelatively dust free mass of carbon pellets is then dried in anyconvenient manner. One convenient method of drying is to pass it`treated pellets discharged from the compacting drum are ready to bepassed immediately to the dryer.

While water is the liquid preferred for use in the spraying step of thisprocess, the water used may be of various kinds andimay contain othersubstances to enhance or modify its effects. By the inclusion ofsolublevadhesive substances or binders inf the spray liquid,`the`se`substances canbe caused to accumulate. on the surface of the' pellets soas to give added strengthto the-shell of?? the pellets Without aifectingthe carbon inside thepellets. For example, various sugars have beenfound to be beneficial, and I have employed advantageously inexpensivegrades of sugarY such asvthose found in cheap molasses. Othersubstancessuch asv dilute cooked starch solutions or gumarabic maybeused inthe spray' liquid.

The accompanying drawing presents-a schematic ow chart to illustrateoneof several possibleways of practicing thisfinvention. In the drawing,A is-an apparatus in which a dry compacting operation is carried oncontinuously, preferably a rotating drum; B is a rotating drum in whichthe dry compacted carbon continuously dischargedfrom A is continuouslytumbled and sprayed supercially with a fine mist of water or aqueoussolution delivered at a limited rate through sprayer C; and D is adryer, e.- g., anV externally heated rotating drum dryer, in which thewater added at B is driven off or extracted from the superficially moistcarbon pellets discharged from drum D so as to yield a productconsisting almost entirely of dry cased carbon pellets which havedistinctiveA combined properties o-f rmness and dispersibility.

Pellets of compacted carbon frequently are subjected to a compressionflow test in order to measure their firmness or resistance tocompression. In this test, a steel cylinder 2 inches in diameter andclosed at one end is rested on the closed end` and iilled to a depth of4 inches with the compacted carbon. A loose fitting piston is placed inthe cylinder and the carbon is pressed by the application of weights tothe piston. Successive lots of carbon are tested until a weight has beenfound which prevents the carbon from flowing when the piston is removedand the cylinder is inverted. The largest weight which can be applied tothe carbon and leave it in a condition to ilow completely from thecylinder is recorded as the flow weight. This weight is a relativemeasure of the ability of the carbon to resist crushing and packing.

The described compression iiow test was used as a measure of rmnessproperties in the following examples which further illustrate thepractice of my invention:

Example I Channel carbon was compacted in a rotating drum by a methodcommonly employed in the carbon black industry. The resulting mass ofdry compacted carbon weighed 24 pounds per cubic foot. Portions of thismass were treated with various amounts of water by spraying the wateronto the surface of the carbon pellets while tumbling the pellets insidea rotating drum. The water was sprayed under pressure of about l to 15pounds per square inch through a nozzle converting it into very inelyatomized or rnist like droplets. The resulting moistened pellets werethen dried at about 300 F. in an externally heated rotating drum.

A further lot of the same carbon was compacted by a conventional wetmethod in which equal parts of carbon and water were employed.

The dust content and the flow weight of each sample of compacted carbonand properties obtained by using each sample in a rubber tread compoundwere determined similarly for all the samples, as follows:

Example II Properties of Rubber Compounds Percent Dust Through Flow MeshWeight Screen Percent Liquid Added Load at 400% Elongation for 60 Min.Cure Liquid used Tensile at Break None.. 0

Water. 20 2.0

0.5% solution of black strap molasses 20 0. 4 60.0

Example Ill A dry furnace black made from a liquid petroleum hydrocarbonat the rate of 10,000 pounds in 24 hours was compacted by passing itthrough a rotating drum 8 feet in diameter and 16 feet long. Thepelletized carbon which weighed 19.5 pounds per cubic foot wasdischarged into a drum 2.5 feet in diameter and 4 feet long, which wasarranged to discharge the treated carbon While maintaining in the drum abed of carbon 7 inches deep. The smaller drum was revolved at 6 R. P. M.while the surface of the carbon tumbling in it was sprayed with a linemist of water at the rate of one pint per minute. This rate amounted to15% of water based on the weight of the carbon. The treated carbon,which appeared to be dry, was discharged into a dryer and thoroughlydried at 320 F. Before being sprayed With water the compacted blackcontained 9.2% of dust passing through a 100 mesh screen, and its owweight was 14.7 pounds. After the Water spraying treatment and drying,the dust content was 4.8% and the iiow weight was 32.5 pounds.

While I have described particular ways of practicing the method of thisinvention, it will be evident that variout other practices can be usedwithout departing from the invention here disclosed and claimed. Forexample, the compacting, spraying and drying can be conducted in asingle long drum, or the spray drum and dryer can be a single drum.Instead of dry compacting the uffy carbon in a rotating drum, otherknown methods of dry compacting can be used. Further, the carbon can bedry compacted and then screened to remove the coarse particles and mostof the dust before the spray treatment, in which case the principalbenefit of the invention consists in the production of pelletized carbonhaving superior dispersion properties along with desired firmness andhandling properties, there being little dust to be taken up on thepellets.

I claim:

l. The method of converting fluffy carbon black into an improvedcompacted form, which comprises cornpacting fluiy carbon blacksubstantially in the absence of liquid until it is formed into drycompacted carbon weighing at least about 18 pounds per cubic foot andconsisting of distinct pellets with less than 20% of dust, thereafterwhile maintaining the material in tumbling motion applying evenly to ita linely divided aqueous liquid in an amount equivalent to from 5 to 25%of the weight of the carbon, and thereafter drying the material toobtain a free owing and relatively dustless but readily disintegratablecompacted carbon.

2. The method of converting fluffy carbon black into an improvedcompacted form, which comprises compacting iiuiy carbon black bytumbling it substantially in the absence of liquid until it is formedinto dry compacted carbon weighing at least about 18 pounds per cubicfoot and containing less than 20% of dust, thereafter While maintainingthe material in motion applying evenly to it a nely divided aqueousliquid in an amount equivalent to from 5 to 25% of the weight of thecarbon, and thereafter drying the material to obtain a free owing andrelatively dustless but readily disintegratable cornpacted carbon.

3. The method of converting uiy carbon black into an improved compactedform, which comprises compacting uiy carbon black by tumbling itcontinuously in the substantial absence of liquid until it is formedinto dry compacted carbon weighing at least about 18 pounds per cubicfoot and containing less than 20% of dust, thereafter while continuouslytumbling the compacted carbon evenly applying to it a inely atomizedspray of aqueous liquid in an amount equivalent to from 5 to 25% of theweight of the carbon, and thereafter drying the material while tumblingit to obtain a free owing and relatively dustless but readilydisintegratable compacted carbon.

4. A method as described in claim 3, said liquid being Water.

5. A method as described in claim 3, said liquid being an aqueoussolution of a substance adhesive to the carbon.

References Cited in the le of this patent UNITED STATES PATENTS2,131,686 Heller et al Sept. 27, 1938 2,306,698 Heller Dec. 29, 19422,502,106 Skogg et al. Mar. 28, 1950 2,550,802 Gholson May 1, 19512,591,024 Sweitzer Apr. 1, 1952

3. METHOD OF CONVERTING FLUFFY CARBON BLACK INTO AN IMPROVED COMPACTEDFORM, WHICH COMPRISES COMPACTING FLUFFY CARBON BLACK BY TUMBLING ITCONTINUOUSLY IN THE SUBSTANTIAL ABSENCE OF LIQUID UNTIL IT IS FORMEDINTO DRY COMPACTED CARBON WEIGHING AT LEAST ABOUT 18 POUNDS PER CUBICFOOT AND CONTAINING LESS THAN 20% OF DUST, THEREAFTER WHILE CONTINUOUSLYTUMBLING THE COMPACTED CARBON EVENLY APPLYING TO IT A FINELY ATOMIZEDSPRAY OF AQUEOUS LIQUID IN AN AMOUNT EQUIVALENT TO FROM 5 TO 25%
 5. AMETHOD AS DESCRIBED IN CLAIM 3, SAID LIQUID BEING AN AQUEOUS SOLUTION OFA SUBSTANCE ADHESIVE TO THE CARBON.